We propose the Probiotic Outcomes on Enteric Microbiotia (POEM) Study, which is a secondary data analysis of previously collected samples from the Trial of Infant Probiotic Supplementation (TIPS) Study to Prevent Markers of Asthma (HL080074). TIPS was designed to examine the effects of daily Lactobacillus casei supplementation in infants for 6 months on the development of early markers of asthma to age three;using a double-blind, placebo controlled study design with 278 infants. In the proposed POEM Study, we will apply a new and novel 16S rRNA PhyloChip microarray approach that is a culture-independent, massively parallel method for simultaneous semi-quantitative detection of bacteria. Use of a PhyloChip microarray on a sample of previously collected stool samples from the TIPS cohort (n=60) presents an opportunity for characterizing how probiotic supplementation altered the intestinal bacterial community. The overall goal of the POEM pilot study is apply a state-of-the-science technology to develop preliminary data to determine the impact of daily probiotic supplementation on the gastrointestinal bacterial community. We will (1) assess the immediate effect and (2) prolonged effect of Lactobacillus supplementation on neonatal intestinal bacterial community during and after a six-month period of supplementation and (3) correlate the effects of the bacterial community composition on the development of early markers of asthma. We hypothesize that Lactobacillus supplementation will change the pattern of intestinal colonization throughout the first year of life. Stool samples have been collected from both groups (at birth, 1, 3, 6, 9 and 12 months of age). We will assess neonatal gut bacterial community composition using a novel 16S rRNA PhyloChip microarray approach, which will assess Lactobacillus colonization, bacterial community structure (presence or absence of specific taxa as inferred from microarray fluorescence intensity), as well as bacterial community dynamics (longitudinal differences in bacterial community development). In this cohort, we have used monthly follow-up to assess potential confounding factors such as exposure to breastfeeding, antibiotics, daycare, siblings, pets and foreign travel. We have data on adherence based on pill counts and stool analyses. We will use multivariate regression methods to test for differences between the control and intervention groups in the extent of Lactobacillus colonization, total bacteria community structure and bacterial community temporal dynamic patterns. Based on the results of this secondary analysis, we will further understand how changes in gut bacterial community may affect the development of atopy. This data will give us an estimate of the overall magnitude and rate of changes in bacterial communities with Lactobacillus supplementation, as well as which of different measures of bacterial community composition are most associated with changes in early markers of asthma. PUBLIC HEALTH RELEVANCE: We propose the Probiotic Outcomes on Enteric Microbiotia (POEM) Study, which is a pilot study to help us understand how probiotic supplementation of newborn babies affects the bacteria that colonize their gut, and how such changes in the bacterial population affect the likelihood of developing early markers of asthma. We will use a new cutting-edge technology, the PhyloChip, to identify bacteria from stool samples of the infants in the study. Data from the POEM pilot study will help us find ways of potentially preventing early signs of asthma through dietary supplementation of infants.